In the computer chip manufacturing industry, it is necessary to test the performance of integrated circuits (IC's) at various points in the manufacturing process, in order to weed out defective components and to monitor the manufacturing process. Various technologies have been employed for this purpose, though all are challenged due to the increasing demands of the IC manufacturing process.
In order to electrically test the circuitry, it is necessary to make contact with pads on the IC, i.e., to “probe” the IC. The probes must be able to align very accurately with the IC pads to be tested, and to provide sufficient current to power the IC as well as provide reliable, low resistance electrical contact at low inductance such that the test signals are not distorted. As IC manufacturing progresses to increasingly smaller geometries, increasing number of transistors, and higher clock frequencies, it challenges the abilities of existing technologies to probe the IC. The smaller geometries result in reduced test pad dimensions, which then require the probes to be better aligned to insure that they do not miss the pads. The increasing number of transistors and higher clock frequencies require that the probes be able to provide an increasing amount of current without burning up or “fusing” the probe, or reducing the probes physical characteristics such as spring force and fatigue life.
IC manufacturers increasingly desire that the IC's be tested at elevated ambient temperature to better simulate worst-case environmental conditions or to perform accelerated life testing. This places an increasing burden on the probe to be able to provide the high current levels at elevated temperatures of 150 degrees Celsius. The increased processing speed of the IC's further requires that the probes have low inductance so as not to distort the clock and signal waveforms that are fed to the IC, and to accurately transfer the waveforms from the IC to the monitoring test equipment.
Some designs in the art include assemblies that combine known conventional vertical buckling beam (VBB) sort interface unit assemblies where the probe head includes an array of curved probes. In such designs, one end of the probes (the “tips”) makes contact with the wafer being tested and the other end (the “head”) makes contact with the array of contact pads on the “C4” side of the space transformer. The curved shape of the wires allows them to flex and act as springs when making contact with the wafer. The compression of the wires allows them to compensate for wafer height and planarity variations without damaging the wafer pads. The requirement that the probes be flexible complicates the manufacturing of the probes and the assembly of the probe head. It also requires that the wires be relatively long (about ¼″) in order to limit the mechanical stress in the wire as it flexes.
There are many known testing devices that do not include the use of carbon nanotubes. For example, U.S. Pat. Nos. 6,906,540, 6,756,797, and 6,297,657, each of which is incorporated by reference as if disclosed herein in its entirety all teach various IC testing devices that do not include the use of carbon nanotube technology. Other assemblies include the use of carbon nanotube bundle probes. Such assemblies can provide unique fabrication challenges and difficult repair challenges.